The present invention relates to differentiators in disk drive read circuits for producing a gate signal to the qualifier comparator.
FIG. 1 shows a disk drive read circuit. A disk 110 is connected to a read/write amplifier 112. A signal is then provided through an automatic gain control circuit 114 in a pulse detector 115 to a filter and differentiator circuit 116. Filter/differentiator block 116 produces a qualified data signal and a gate signal. These are provided to a qualifier comparator circuit 118. The gate signal output provided to qualifier comparator 118 is produced by a differentiator in circuit 116. The cutoff frequency of this differentiator will determine the rise time of the gate signal, and thus the time at which the gate signal will become active. When the gate signal is received, the pulse detector 118 will compare the qualified data signal with a signal threshold level to determine whether the data is a digital zero or digital one. The result will then be passed on to a data separator circuit 120 which will then provide the output data for use by a computer or other device.